The invention relates to an article conveying system utilizing a conveying train including a tug or locomotive and sequentially connected article conveying cars, the cars including a chassis and article tray. In particular, the invention relates to an improved chassis for the article conveying cars.
Automated article conveying and sorting systems are widely used for receiving, transporting and discharging articles by and between receiving and discharge stations. Such systems are widely used for transporting and classifying articles in such operations as package shipment and delivery systems, warehouse storage and retrieval operations, and bulk postage handling operations.
In some applications, powered belt-type or roller conveyors are utilized for article transportation and sorting operations. Another type of article transportation and sorting system utilizes track mounted article conveying cars driven by a belt or chain which is powered by a stationary drive motor. Yet another system utilizes a conveying train including a powered tug or locomotive and sequentially connected article conveying cars for moving articles around a path including loading and discharge stations. In some cases the article conveying cars are equipped with tilting trays for receiving and discharging articles at various locations around the perimeter defined by the track. Mechanical or electromechanical devices such as cams, limit switches and location sensors may be utilized to control the tilting action of the trays during the transportation operation.
The operation of the article conveying train may be controlled by one or more microprocessors and a microprocessor may be employed to monitor and control the operation of the conveying train. Such a system may employ a stationary microprocessor and a mobile microprocessor mounted on the tug or locomotive with appropriate communication devices as well as various sensors, actuators and control devices for monitoring and controlling the operation of the system. One such system is disclosed in U.S. Pat. No. 5,632,589, titled xe2x80x9cApparatus for Centralized Mechanical and Systems Control in a Material Handling System,xe2x80x9d issued May 27, 1997, and assigned to Symorex, Inc. Another such system is disclosed in U.S. Pat. No. 5,662,045, titled xe2x80x9cLocomotive for Material Handling Train,xe2x80x9d issued Sep. 2, 1997, and assigned to Symorex, Ltd., while another such system entitled xe2x80x9cTrack for Sortation Handling Equipmentxe2x80x9d is disclosed in U.S. Pat. No. 5,555,814, issued Sep. 7, 1996, and assigned to Symorex, Inc. A train and track with a locomotive including a microprocessor for keeping track of position, regulating speed and controlling dumping is disclosed in U.S. Pat. No. 5,018,929 to Hartlepp, issued May 28, 1991. The disclosures of U.S. Pat. Nos. 5,632,589; 5,662,045; 5,555,814 and 5,018,928 are incorporated herein by reference for all purposes.
In an article sorting system utilizing a powered tug or locomotive to pull consecutively coupled article conveying cars, a monorail track is often used. In order to traverse a continuous path between loading and discharge stations, the track must incorporate arcuate sections. Additionally, depending upon the particular control system used, the speed of the conveying train must be closely controlled in order to effect the proper sequencing of loading and unloading articles. For example, if the unloading sequence is keyed or triggered by the expected location of the train or a particular article conveying car at a given time, the failure of the train to be in the proper position at the designated time may result in overloading or mis-loading a car, damaged articles or packages, clogged or jammed auxiliary chutes or conveyors and system downtime. Thus, close control of the article conveying train""s speed can be a critical factor in the operation of such a system.
The cars utilized in a tug or locomotive powered train in an article conveying system as described above typically employ at least two sets of wheels for traversing the monorail track. The two sets of wheels are normally located adjacent to opposing ends of the car. Outrigger and guide wheels may also guide and stabilize the car as it traverses the monorail. In order to provide the necessary stability to the car, especially if the car is equipped with a tilting tray for discharging articles, the car must maintain a fixed position relative to the monorail track. Usually the wheels of the car are depended upon to maintain the car in the proper position relative to the track. However, if the wheels are fixed in position relative to the track and the tilting tray mechanism carried by the car, additional frictional forces will be generated between the wheels and the track as the car traverses arcuate portions of the track. The additional frictional forces generated as a plurality of such cars are pulled through an arcuate section of track will tend to slow the train, thereby interfering with operation of the conveying and sorting system. The extent of the frictional forces will depend upon the relative spacing of the car wheels along the car chassis, the radius of curvature of the arcuate track section, the type of wheels used and other factors. The problem is accentuated when a monorail track is used due to the close tolerances between the car wheels and rail required to give the car the required stability. Although the problem may be alleviated through the use of a segmented, articulated car chassis permitting independent movement of the different sections of the car, such cars are more complicated and expensive to produce and maintain and present additional problems. Additionally, article conveying cars with segmented chassis may not be suited for use in certain applications where the rigidity of conventional chassis is required.
Other problems and concerns associated with the prior art article conveying mechanisms involve the discharge mechanism used to discharge articles at various locations around the perimeter defined by the track. Such mechanisms have tended to be complex and not as reliable as desired. For example, a cross-belt sorter including an endless loop of linked wheeled chassis members which include hub-mounted generators attached to at least one of the wheels of each chassis member is disclosed in U.S. Pat. No. 5,690,209 to Kofoed, issued Nov. 27, 1997. Kofoed""s carriers are preferably cross-belt units driven by on-board a.c. motors and each carrier is equipped with circuitry for controlling the motor. Additionally, a battery is provided on each carrier.
In one embodiment, the invention comprises a passive discharge apparatus adapted for mounting on a trolley for transporting articles along the path of a track, the apparatus being adapted to receive and discharge articles at a selected location. In one aspect, the passive discharge mechanism includes a conveyor, mounted for movement in a direction transverse to the track and an arm coupled to the conveyor for engaging a moveable member positioned adjacent to the track. A flexible connector is used to couple the arm to the conveyor, the connector translating movement of the arm upon engagement of the member into transverse movement of the conveyor for discharging articles carried by the apparatus without the need for a powered drive unit for the conveyor. In another aspect, the passive discharge mechanism comprises a titling tray discharge apparatus.
In either aspect, the passive discharge mechanism may engage a moveable member mounted adjacent to the rail on which the trolley operates. In this case the trolley is provided with on-board intelligence, i.e., a microprocessor. Thus, the member may be actuated by a signal from the on-board microprocessor carried by the trolley that communicates with an external controller. The external controller communicates the destination of an article as the article is loaded on the trolley, and the microprocessor utilizes sensing devices to determine when it is approaching the selected destination. The on-board microprocessor then generates a signal, actuating the movable member to engage the passive discharge apparatus, discharging the article.
The present invention also provides an improved truck for supporting a car on a rail structure, such as a trolley car forming part of a conveyor system. Such a truck includes a carriage, a yoke connected to the carriage by a rotatable support, such that the yoke can rotate in a horizontal plane relative to the carriage, a plurality of guide wheels, fixtures that mount each wheel to the yoke optionally at horizontally offset positions with predetermined spacing to conform to the rail structure, such that rotation of the yoke relative to the carriage causes the wheels to move in unison to conform to a curve in the rail structure. An articulated yoke of the invention is specially adapted for supporting one or more wheels on opposite sides of a monorail. A conventional material carrying device may be mounted on the carriage. Such a material carrying device may be as simple as a horizontal platform, or more elaborate, such as a tilt-tray or transverse belt discharge mechanism. The fixtures that mount the wheels to the yoke are preferably not mounted on casters, i.e., rotatable axles. Instead, such wheels are mounted to the yoke using a fixture that does not substantially swivel. However, the yoke uniting the wheels is mounted to the carriage in such a manner that the yoke and wheels can swivel in unison relative to the carriage about a xe2x80x9cvirtual axlexe2x80x9d which may be offset from the actual vertical axes of the individual wheels. Such an arrangement, particularly when a pair of yokes are mounted at front and rear portions of the carriage, provides a rail-borne car which moves smoothly around curves yet is securely mounted in its associated rail or rails.
In one embodiment, a trolley car for conveying articles along a monorail having arcuate portions includes a rigid frame having a longitudinal axis and opposed ends. A pair of rotatable yokes are each coupled to the frame adjacent to the opposed ends of the frame for rotational movement around an axis perpendicular to the longitudinal axis as the trolley car travels along an arcuate portion of the monorail. Each of the yokes has a pair of opposed arms extending from the mainframe and a pair of guide wheels are mounted on each of the opposed arms for rotational contact with a guide surface of the monorail. The trolley car also includes a load bearing wheel mounted adjacent to each of the opposed ends of the rigid frame. Each of the load bearing wheels is moveable around an axis perpendicular to the longitudinal axis for rotational movement around the axis as the trolley car travels along an arcuate portion of the monorail. The load bearing wheels are mounted on an uppermost portion of the frame, extend through the frame and contact an upper load bearing surface of the monorail.
In another embodiment, a chassis for a supporting a trolley car along a monorail has a central vertical axis includes a rigid frame having a longitudinal axis. The frame includes a plurality of openings arranged around an axis perpendicular to the longitudinal axis of the chassis frame.
At least one rotatable yoke including opposing arms extending from the frame is coupled to the frame for rotational movement around the perpendicular axis as the chassis travels along an arcuate portion of a monorail. A plurality of couplers such as bolts, screws or rivets extend through the openings retaining the yoke for rotation around the perpendicular axis. The chassis also includes at least one rail guide wheel mounted on each of the opposing arms for guiding the chassis during movement along the monorail and at least one load bearing wheel coupled to the frame for rotation along a top surface of the monorail. The load bearing wheel supports the chassis as the trolley car moves along the monorail. At least one stabilizing outrigger wheel is coupled to the frame in order to stabilize the frame against swaying or rotational movement around the longitudinal axis of the chassis during movement along the rail.
In another embodiment, a truck for supporting a trolley car along a monorail having a central vertical axis includes a centrally positioned load bearing wheel. The load bearing wheel contacts and rotates along an upper surface of the rail to support the trolley car. The truck also includes a yoke mounted for rotation around a central vertical axis of the rail with opposing outwardly inclined arms. At least one guide wheel is mounted on each of the inclined arms for rotating along an upper inclined guide surface of the rail. The truck includes a support plate for supporting the yoke and a plurality of fasteners coupling the yoke and support plate for movement relative to the support plate. Outrigger wheels are also provided for minimizing or eliminating any sway as the car moves along the rail.